Direction: Find the word or words that can substitute for the underlined words.

The study of plant life is taught to all school children in secondary classes.

The correct answer is 'Botany​.'
Key Points 
 

• Biology: the scientific study of living things. (सजीवों का वैज्ञानिक अध्ययन; जैविकी, जीवविज्ञान)
  • For example: He is studying biology, chemistry and mathematics in the hope of becoming a doctor.
• Notes: The greet word bio means life and logos means to study, so biology means study of life. 
• From the above meaning it can be concluded that the study of plant life is called biology. 

Therefore, the correct answer is "Option 2". 

Additional Information

• Let us see the meanings of the other given options:
  • Zoology: the scientific study of animals. (जंतुविज्ञान, प्राणीविज्ञान)
  • Botany: the scientific study of plants. (वनस्‍पति-शास्‍त्र)
  • Sociology: the study of human societies and social behaviour. (समाजशास्‍त्र; मानव समाजों और सामाजिक व्‍यवहार का अध्ययन)